Such a treat to go through the space museum with Scott Manley, with his encyclopedic knowledge on every artifact. Video here, quite a treat!
I asked which was his favorite, and he chose my RL10, the second one ever built. It has flown for over 60 years, and powers ULA’s new rocket too.
The bell is composed of 360 pipes that route liquid hydrogen fuel down and back before combustion to keep the nozzle from melting (regenerative cooling).
This engine uses a clever expander cycle with gear-coupled fuel and oxidizer turbo pumps, a design that has not been used on any other hydrogen engine. The phase change of the hydrogen fuel from liquid to gas powers both the fuel and oxidizer cyro pumps (just above our fingers).
It has carried spacecraft the moon and the sun and every planet in our solar system and beyond. In 1959, hydrogen was considered a dangerous and unpredictable fuel, and little of it was available for research. “It was our trip to Florida to see the RL10 firing that gave me confidence to use hydrogen for Apollo.” — Werner Von Braun in the book Advanced Engine Development at Pratt & Whitney
On my left (in the red frame) is a spare engine from the Viking Mars spacecraft, and to his right is an early Block 1 prototype of the Apollo CSM SPS engine from 1964.
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